Method, system and device for maintaining user service continuity

ABSTRACT

A method, a system and a device for maintaining user service continuity are provided in an embodiment of the present invention. The method includes prohibiting a UE from accessing a forbidden network before handover is complete when the UE needs to perform network handover if the UE adopts a SIM access technology, thus avoiding service interruption of a SIM user due to access to an incorrect network. A system and a device for maintaining user service continuity are provided in an embodiment of the present invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/914121, filed on Oct. 28, 2010, which is a continuation ofInternational Application No. PCT/CN2009/070113, filed on Jan. 12, 2009.The International Application claims priorities to Chinese PatentApplication No. 200810066885.X, filed on Apr. 28, 2008 and ChinesePatent Application No. 200810145545.6, filed on Aug. 1, 2008. Theafore-mentioned patent applications are hereby incorporated by referencein their entireties.

FIELD OF THE INVENTION

The present invention relates to the field of communicationstechnologies, and in particular, to a technology for maintaining userservice continuity.

BACKGROUND OF THE INVENTION

With the constant development of communications technologies, a user canaccess a core network of an operator through any of the following accessmethods: Global System for Mobile communications/Enhanced Data rates forGSM Evolution Radio Access Network (GERAN), Universal MobileTelecommunication System Terrestrial Radio Access Network (UTRAN), andevolved UTRAN (eUTRAN).

When a user moves between networks, to maintain continuity of userservices, seamless handover between access technologies such as GERAN,UTRAN, and eUTRAN is required.

In the prior art, users who adopt a Subscriber Identity Module (SIM) orrun SIM applications on a Universal Integrated Circuit Card (UICC) arecalled SIM users. When a SIM user communicates in a UTRAN or GERANnetwork and moves to a border between an eUTRAN and the UTRAN or GERAN,if the signal strength of the eUTRAN is stronger than that of otheraccess networks, or if a service requires, the source network may selectthe eUTRAN as the target network for network handover and switch theuser to the eUTRAN temporarily through a normal handover process. Inthis case, the SIM user can temporarily use the resources of the corenetwork and then execute Authentication and Key Agreement (AKA). TheSIM, however, does not support AKA. Therefore, if the SIM user isidentified during this process, the connection of the SIM user to theeUTRAN is terminated.

During the implementation of the present invention, the inventordiscovers the following disadvantages in the prior art: The existingtechnology implements the function of forbidding a SIM user to access aneUTRAN. After the SIM user temporarily switches to the eUTRAN, theeUTRAN rejects the access of the SIM user according to the AKA result.At this time, the SIM user is disconnected from the originally availablenetwork, which leads to service interruption.

SUMMARY OF THE INVENTION

A method, a system and a device for maintaining user service continuityare provided in an embodiment of the present invention, to avoid serviceinterruption of a SIM user due to access to a forbidden network andmaintain user service continuity.

A method for maintaining user service continuity is provided in anembodiment of the present invention. The method includes:

-   -   when a User Equipment (UE) needs to perform network handover,        prohibiting the UE from accessing a forbidden network before the        network handover is complete if the UE adopts a Subscriber        Identity Module (SIM) technology for access; and    -   selecting an accessible target network for the UE.

A system for maintaining user service continuity is provided in anembodiment of the present invention. The system includes:

-   -   a judging unit, configured to judge whether a UE is a SIM user        when the UE needs to perform network handover; and    -   a handling unit, configured to prohibit the UE from accessing a        forbidden network before the network handover is complete when        the judging unit determines that the UE is a SIM user; and        select an accessible target network for the UE.

A device for maintaining user service continuity is provided in anembodiment of the present invention. The device includes:

-   -   a judging unit, configured to judge whether a UE is a SIM user        when the UE needs to perform network handover; and    -   a handling unit, configured to prohibit the UE from accessing a        forbidden network before the network handover is complete when        the judging unit determines that the UE is a SIM user.

A method for maintaining user service continuity is provided in anotherembodiment of the present invention. The method includes:

-   -   prohibiting a UE in the Idle state from accessing a forbidden        network during location update of the UE if the UE adopts a SIM        access technology when the UE moves between networks.

A Mobile Management Entity (MME) is provided in an embodiment of thepresent invention. The MME includes:

-   -   an obtaining unit, configured to obtain information about a user        type of a UE or information about a forbidden network type,        wherein the information about the forbidden network type        indicates the information about a type of network that the UE        cannot access; and    -   a handling unit, configured to implement, when the UE in the        Idle state moves between networks, handling, according to the        information about the user type of the UE or information about        the forbidden network type obtained by the obtaining unit,        wherein the handling includes prohibiting the UE from accessing        a forbidden network during location update of the UE when the UE        is a SIM user.

Another method for maintaining user service continuity is provided in anembodiment of the present invention. The method includes:

-   -   a UE shields a forbidden network type according to a user        identity module type.

Through comparison, it can be seen that any one of the precedingtechnical solutions has the following advantages or beneficial effectsover the prior art:

In an embodiment of the present invention, before a SIM user accesses ortemporarily accesses to a forbidden network, such as an eUTRAN, that is,before handover is complete, a judgment is made about a user type orforbidden network type. If the UE is a SIM user, and a target networkdoes not allow access of a SIM user, the UE is prohibited from handingover to the target network, and another target network is selected forhandover. In this way, service interruption occurring due to incorrectaccess of the SIM user to the eUTRAN is avoided, and user servicecontinuity is maintained. In addition, after a UE in the Idle statemoves between networks, the UE can be prohibited from accessing aforbidden network during location update, and this avoids serviceinterruption caused by the following scenario: After a SIM user in theIdle state moves to the eUTRAN and transits from the Idle state to theConnected state, the network triggers AKA, but the SIM card does notsupport AKA. As a result, user service continuity can be maintained tocertain extent.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to some accompanyingdrawings as follows:

FIG. 1 is a flowchart of a method for maintaining user servicecontinuity according to an embodiment of the present invention;

FIG. 2 is a flowchart of a method for maintaining user servicecontinuity according to a first embodiment of the present invention;

FIG. 3 is a flowchart of a method for maintaining user servicecontinuity according to a second embodiment of the present invention;

FIG. 4 is a flowchart of a method for maintaining user servicecontinuity according to a third embodiment of the present invention;

FIG. 5 is a flowchart of a method for maintaining user servicecontinuity according to a fourth embodiment of the present invention;

FIG. 6 is a flowchart of a method for maintaining user servicecontinuity according to a fifth embodiment of the present invention;

FIG. 7 is a flowchart of a method for maintaining user servicecontinuity according to a seventh embodiment of the present invention;

FIG. 8 is a flowchart of a method for maintaining user servicecontinuity according to an eighth embodiment of the present invention;

FIG. 9 shows a mobile communication system provided according to a ninthembodiment of the present invention;

FIG. 10 shows a device according to a tenth embodiment of the presentinvention; and

FIG. 11 shows an MME according to an eleventh embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To clarify the purpose, technical solution, and advantages of theembodiments of the present invention, the embodiments of the presentinvention are described with drawings as follows.

A method for maintaining user service continuity is provided in anembodiment of the present invention. As shown in FIG. 1, the methodincludes:

Step 101: A judgment is made about whether a UE adopts a SIM technologyfor access when the UE needs to perform network handover.

Step 102: The UE is prohibited from accessing a forbidden network beforethe network handover is complete if the UE adopts the SIM technology foraccess.

Step 103: An accessible target network is selected for the UE.

According to the preceding solution, embodiments that support thesolution are described as follows.

An entity at a network side involved in a first embodiment of thepresent invention includes a source Radio Network Controller (RNC) orsource Base Station Controller (BSC), a source Serving GPRS Support Node(SGSN), and a target MME, as shown in FIG. 2.

Step 201: When a UE needs to perform network handover, the source RNC orsource BSC sends a Relocation/Handover Required to the source SGSN.

Step 202: The source SGSN judges whether the UE is a SIM user.

The method for obtaining the user type can be as follows: A HomeLocation Register (HLR) or Home Subscriber Server (HSS) sends a usertype indication to an SGSN. The specific sending process can be asfollows: After receiving an authentication vector request from the SGSN,the HLR/HSS sends an authentication vector that carries the user typeindication to the SGSN; or the HLR/HSS inserts the user type, such asSIM user and USIM user, into user subscription data to the SGSN.

The method for obtaining the user type may also be as follows: The SGSNinfers the user type according to the authentication vector typeobtained from the HLR/HSS. For example, if the SGSN obtains a quintetfrom the HLR/HSS, the SGSN determines that the user is a USIM user; ifit is a triplet, the SGSN determines that the user is a SIM user.

It should be noted that when the UE performs inter-SGSN handover or cellreselection, a new SGSN needs to obtain the user type information froman original SGSN. The implementation method may be as follows: Duringhandover preparation, the original SGSN sends the user type informationto the new SGSN, or the new SGSN obtains the user type information whenobtaining the UE context from the original SGSN during location updateor route update of the UE.

It should be noted that the original SGSN in an embodiment of thepresent invention indicates the SGSN that is adopted before inter-SGSNhandover or cell reselection of the UE, and the new SGSN indicate theSGSN that the UE belongs to after inter-SGSN handover or cellreselection of the UE.

The method for obtaining the user type may also be as follows: The UEcarries the user type information, for example, information aboutwhether the UE is a SIM user, in an initial layer 3 message, such as anattachment request, to enable the SGSN to know the user type of the UE.

If it is judged that the UE which needs to perform network handover isnot a SIM user in step 202, the process proceeds to step 203 to send aRelocation/Handover Required message to a target MME, and the subsequentprocedure is performed. The non-SIM user, however, may be rejected toaccess the target network because it is not registered with the targetnetwork. If the UE is a SIM user and the target network is a forbiddennetwork for the UE, the process proceeds to step 204 to send aRelocation Preparation Failure message to the source RNC or source BSC.Upon receiving of this message, the source RNC or source BSC can selectanother access network.

In this embodiment, during handover preparation, when aRelocation/Handover

Required message is sent to the source SGSN, the source SGSN judges theuser type and determines whether to access the UE to an eUTRAN. In thiscase, the service interruption occurring due to incorrect access of aSIM user to an eUTRAN is avoided in advance and the service continuityis maintained. At the same time, with the method in this embodiment, theSIM user does not have the chance of using the eUTRAN, and this avoidssecurity risks on the eUTRAN.

The second embodiment is basically the same as the first embodiment. Thedifference is as follows: In the second embodiment, the target MMEjudges the UE type, as shown in FIG. 3.

Step 301: The procedure is the same as the procedure in step 201 in thefirst embodiment.

Step 302: After receiving the Relocation/Handover Required message, thesource SGSN sends a Relocation/Handover Required message to the targetMME and sends the user type to the target MME. The user type may becarried in the Relocation/Handover Required message, or sent as aseparate message.

The method for obtaining the user type by the source SGSN is the same asthat in step 202 in the first embodiment.

Step 303: After receiving the Relocation/Handover Required message, thetarget MME judges, according to the received user type, whether the UEis a SIM user.

If it is judged that the UE which needs to handover to the eUTRAN is aSIM user in step 303, the process proceeds to step 304 to return anerror message to the source SGSN. In step 305, the source SGSN returnsthe handover failure message to the source RNC or source BSC. Then, thesource RNC or source BSC selects another access network for the UE.

In this embodiment, the SGSN obtains and forwards the user type. Whenthe Relocation/Handover Required message is sent to the target MME, thetarget MME determines according to the user type whether to access theUE to the eUTRAN, and this prevents service interruption due toincorrect access to the eUTRAN and maintains the service continuity. Atthe same time, through the method in this embodiment, the SIM user doesnot have the chance of using the eUTRAN, and this avoids bringingsecurity risks on the eUTRAN.

The main difference between the third embodiment and the first andsecond embodiments is as follows: In the third embodiment, the UE sendsthe user type to the network side. That is, the basis for judging the UEtype is different. See FIG. 4.

Step 401: The UE sends a type identity to the source RNC or source BSC.

This type identity may be carried in a Radio Resource Control (RRC)connection request or completion message during RRC connectionestablishment, or carried in other RRC messages, such as a security modecommand completion message.

It should be noted that the type identity in the embodiment of thepresent invention is a parameter used to uniquely identify a UE type.The UE type may be SIM or USIM. This parameter may be a field thatidentifies the user, or an identity recognized by the network side andUE. The type identity is a name adopted merely to facilitatedescription. This name cannot confine the applicable scope of theembodiment of the present invention. That is, in certain systems, theexpression of type identity may not be adopted. However, it cannot bedeemed that the technical scheme in the embodiment of the presentinvention does not apply to such systems.

Step 402: When the UE needs to perform handover between GERAN and UTRAN,the source RNC or source BSC sends the Relocation/Handover Requiredmessage that carries the user type identity.

Step 403: After receiving the Relocation/Handover Required message andtype identity, the source SGSN determines whether switch the UE to thetarget network according to whether the UE is a SIM user.

If it is judged that the UE which needs to perform network handover isnot a SIM user in step 403, the process proceeds to step 404 to send aRelocation/Handover Required message to a target MME, and subsequentprocedure proceeds. The non-SIM user, however, may be rejected to accessthe target network because it is not registered with the target network.If the UE is a SIM user, and the target network is a forbidden networkfor the UE, the process proceeds to step 405 to send a RelocationPreparation Failure message to the source RNC or source BSC. Uponreceiving of this message, the source RNC or source BSC can selectanother access network.

It should be noted that an alternative scheme of this embodiment may beas follows: The source SGSN does not judge the user type, but forwardsthe Relocation/Handover Required message and type identity to the targetMME, which judges the user type; or after receiving the type identity ofthe UE, the source RNC or source BSC rules out the forbidden networksduring handover decision phase. For example, if the UE is a SIM user,the source RNC or source BSC does not select a network that forbids SIMaccess, such as eUTRAN.

In this embodiment, the UE reports the type identity to the networkside, facilitating the entity at the network side to directly read theidentity and determine the user type indicated by this identity. As aresult, service interruption due to incorrect access of a SIM user to aneUTRAN can be prevented during handover decision or handoverpreparation, and this maintains service continuity of the UE. Inaddition, as stated in the benefits of the previous embodiments, thesecurity risks on the eUTRAN can be avoided.

The fourth embodiment of the present invention is basically the same asthe previous embodiments. The main difference is that: The network sideinquires the UE, and subsequent actions depend on the response of theUE. See FIG. 5.

Step 501: When the UE needs to perform network handover, the source RNCor source BSC sends an inquiry message to the UE. This message may carrythe type identity of the target network.

Step 502: The source RNC or source BSC receives a response from the UE.

The response can be sent by the UE based on the judgment of the UE aboutwhether to access the target network. If the UE is a SIM user, and thetarget network is an eUTRAN, access rejection information is carried inthe response. In this case, the source RNC or source BSC needs to selectanother target network. If the UE judges that it can access the targetnetwork, the response carries the access approval information. In thiscase, the source RNC or source BSC performs network handover accordingto the normal handover flow.

The response may also be as follows: The UE does not make the precedingjudgment, but directly reports its user type or forbidden networkinformation to the network side.

In this embodiment, the UE may actively choose whether to access thenetwork, or the network side determines, according to the response fromthe UE, whether to allow the UE to access the eUTRAN, and thus preventsincorrect access of a SIM user to an eUTRAN, and maintains servicecontinuity.

In the fifth embodiment of the present invention, the source RNC orsource BSC obtains a Forbidden List or user type information from thecore network, as shown in FIG. 6.

Step 601: When the UE needs to perform network handover, the source RNCor source BSC sends a Relocation/Handover Required message to the sourceSGSN.

Step 602: The source SGSN sends forbidden network type or the user typeto the source RNC or source BSC.

Forbidden network type may include one or more items. The SGSN can senda Forbidden List to the source RNC or source BSC.

The method for obtaining forbidden network types by the SGSN can beincluding a Forbidden List in subscription information. When the UEregisters with the SGSN, the SGSN obtains the Forbidden List in thesubscription information from the HLR or HSS, and sends the ForbiddenList as secure context during handover or cell reselection. TheForbidden List may also be generated by the SGSN according to the usertype.

Step 603: The source RNC or source BSC determines whether the UE canaccess a network according to the received user type information, orreads the forbidden networks of the UE from the received Forbidden List.In this way, the source RNC or source BSC selects an accessible networkfor handover.

Step 604: The source RNC or source BSC selects an accessible network forhandover, and sends a Relocation/Handover Required message again.

It should be noted that this Forbidden List can be sent by the sourceSGSN to the source RNC or source BSC before the UE needs to performnetwork handover. When the UE needs to perform network handover, theForbidden List can be referred to determine accessible networks for theUE, and then the source RNC or source BSC can send a Relocation/HandoverRequired message to the source SGSN.

In this embodiment, a Forbidden List is established to prevent the UEfrom accessing forbidden networks. This list can cover all the networksthat the UE cannot access, thus correctly preventing a SIM user fromaccessing an eUTRAN in time and maintaining service continuity.

The main difference between the sixth embodiment and the fifthembodiment is as follows: The forbidden network types are not judged bythe network side, but on the UE to prevent a SIM user form accessing aneUTRAN.

The detailed procedure can be as follows: A Forbidden List is manuallyset up on the UE. If the UE is a SIM user, eUTRAN is included in theForbidden List of the UE. In this way, the UE does not need to detectsignals of an eUTRAN during each power-on, and does not measure thefrequency band of the eUTRAN during each inter-frequency measurement, ornotifies the network side in the measurement report that it cannotdetect an eUTRAN cell. In this way, the network side does not select aneUTRAN as the target network, thus preventing a SIM user from accessingthe eUTRAN.

The preceding setting flow can be realized by the UE. That is, the UEobtains the user type. If the user type indicates a SIM user, networksthat forbid SIM access, such as an eUTRAN, are automatically added tothe Forbidden List. Or, the UE judges a forbidden network when receivinga measurement command, and implements subsequent processing.

It should be noted that the Forbidden List in this embodiment means alist that is used to store the forbidden networks of the UE. This nameis merely adopted to facilitate description. This name cannot confinethe applicable scope of the embodiment of the present invention. Thatis, in certain systems, the expression of Forbidden list is not adopted.However, it cannot be deemed that the technical scheme in the embodimentof the present invention does not apply to such systems.

The main difference between the seventh embodiment and the fifthembodiment is as follows: In this embodiment, before the UE needs toperform network handover, the network side sends the user type orforbidden network types of the UE to the source RNC or source BSC, asshown in FIG. 7.

Step 701: An RRC connection is established between the UE and the sourceRNC or source BSC.

Step 702: The UE sends an initial layer 3 message, such as attachmentrequest, service request, and location or route update request, to thecore network.

Step 703: Alternatively, the source SGSN initiates a key negotiation andauthentication flow, and before that, if no unused local authenticationvector is available, the authentication vector needs to be obtained fromthe HLR or HSS.

Step 704: The source SGSN sends forbidden network type or the user typeto the source RNC or source BSC.

The source SGSN can carry the forbidden network type or user type in aRadio Access Network Application Part (RANAP) security mode commandmessage, or other interface messages, such as a radio access bearerassignment message. It should be noted that this embodiment does notconfine the interface messages. Those skilled in the art can implementthe present invention by using other messages, such as a COMMON IDmessage. For the sending mode, see the relevant description in the fifthembodiment of the present invention.

It should be noted that, if a radio access bearer assignment message isused to carry the forbidden network type or user type, an informationelement (IE) in the message, such as the Service Handover IE, can beused to inform the source RNC or source BSC whether the UE can access aneUTRAN. For example, the values of the IE include: Handover to eUTRANshould be performed, Handover to eUTRAN should not be performed, andHandover to eUTRAN shall not be performed.

During handover, if the RNC or BSC that governs the UE is changed, thesource SGSGN adds the Service Handover IE to the relocation request thatis sent to the target RNC or BSC to inform the target RNC whether the UEcan access an eUTRAN.

It should be noted that the method for obtaining the user typeinformation about whether the UE is a SIM user by the SGSN includes:sending, by the HLR or HSS, an authentication vector or usersubscription data to the SGSN, and obtaining, by the SGSN, the user typeinformation carried in the authentication vector or user subscriptiondata; or, inferring, by the SGSN, the user type information of the UEaccording to the authentication vector type obtained from the HLR orHSS; or, obtaining, by the RNC or BSC, the user type information carriedin an RRC message sent by the UE to the network side, and sending, bythe RNC or BSC, the user type information to the SGSN; or, obtaining, bythe new SGSN, the user type information of the UE from the original SGSNduring inter-SGSN handover or cell reselection; or, sending, by the UE,an initial layer 3 message that carries the user type information to theSGSN.

Further, it should be noted that the method for obtaining theinformation about forbidden network type by the SGSN includes: inferringthe forbidden network type according to the user type information; or,obtaining, by the new SGSN, the information about forbidden network typefrom the original SGSN during inter-SGSN handover or cell reselection;or, obtaining the information about forbidden network type from the usersubscription data.

Step 705: The source RNC or source BSC saves the obtained forbiddennetwork type or the user type.

It should be noted that, before handover to an eUTRAN, if handoverinside a UTRAN or a GERAN, or between UTRAN and GERAN occurs,alternatively, the source RNC or source BSC before handover (originalRNC or BSC for short) needs to transfer the obtained forbidden networktype or user type to the source RNC or source BSC after handover (newRNC or BSC for short).

Step 706: The source RNC or source BSC sends the response correspondingto step 704 to the core network.

Step 707: When the UE needs to perform handover, the source RNC orsource BSC judges accessible networks of the UE according to thereceived user type information or forbidden network type, or obtains theforbidden networks of the UE from the received Forbidden List. In thisway, the source RNC or source BSC selects an accessible network forhandover.

In this embodiment, the network side selects an accessible network forthe UE before the UE needs to perform network handover. Thus, the UE candirectly access the accessible network during network handover,maintaining user service continuity and improving network handoverefficiency.

FIG. 8 is a flowchart of a method for maintaining user servicecontinuity in an eighth embodiment of the present invention. Comparewith the third embodiment, the method for maintaining user servicecontinuity in the eighth embodiment differs in that the UE moves to aneUTRAN in the Idle state. The method for maintaining user servicecontinuity in the eighth embodiment includes:

Step 801: The UE sends a Tracking Area Update (TAU) Request to thetarget MME after moving to an eUTRAN.

Step 802: The target MME sends a context request to the source SGSN toobtain the relevant information of the UE.

Step 803: The source SGSN returns a context response to the target MME.This response can include the user type or forbidden network type of theUE.

Step 804: The target MME makes a judgment according to the user type orforbidden network type of the UE in the context response. If the UE is aSIM user or is forbidden from accessing an eUTRAN, step 805 is executed.

Step 805: The target MME sends a TAU rejection message to the UE toreject the SIM user from accessing the eUTRAN.

In this embodiment, alternatively, the UE can report the user type orforbidden network type in the TAU message in step 801 to the target MMEso that the target MME can decide whether to send the TAU rejectionmessage in step 804 according to the user type or forbidden networktype. For example, if the UE is a SIM user or the forbidden network typeinclude eUTRAN, the target MME sends the TAU rejection message to the UEto reject the SIM user from accessing the eUTRAN.

Further, in this embodiment, after receiving the TAU rejection message,the UE can select another accessible network, thus avoiding serviceinterruption caused by the following scenario: After a SIM user in theIdle state moves to the eUTRAN and transits from the Idle state to theConnected state, the network triggers AKA, but the SIM card does notsupport AKA. As a result, user service continuity can be maintained tocertain extent.

In this embodiment, the network side selects an accessible networkduring location update so that the UE can use accessible networkresources directly after transiting from the Idle state to the Connectedstate, thus maintaining user service continuity and improving userexperience.

A mobile communication system involved in an embodiment of the presentinvention is described as follows. This system can implement the stepsin the methods in the preceding embodiments. It is understandable thatthe system in this embodiment of the present invention can include otherentities that implement communication functions. Those technologies thatmay be revealed by the existing technology and those standardizedtechnologies in the communication field are not described here. Topresent the implementation scheme in this embodiment, only the majorparts of this system are described. As shown in FIG. 9, this systemincludes:

-   -   a judging unit 901, configured to judge whether a UE is a SIM        user when the UE needs to perform network handover; and    -   a handling unit 902, configured to prohibit the UE from        accessing a forbidden network before the network handover is        complete when the judging unit determines that the UE is a SIM        user, and select an accessible target network for the UE.

It should be noted that this judging unit can be placed at the terminalside and configured to make a judgment according to the user typeinformation or forbidden network type from the terminal side, or placedat the network side and configured to make a judgment according to theuser type information or forbidden network type from the network side.

A UE is provided in the ninth embodiment of the present invention. TheUE includes: a judging unit, configured to judge user identity moduletype; and a handling unit, configured to shield a forbidden network typeaccording to the user identity module type. The handling unit canfurther include: a forbidding measuring unit, configured to forbidmeasuring the forbidden network type.

FIG. 10 shows a device in a tenth embodiment of the present invention.The device includes: a judging unit 1001, configured to judge whether aUE is a SIM user when the UE needs to perform network handover; and ahandling unit 1002, configured to forbid the UE from accessing forbiddennetworks before handover completes when the judging unit judges that theUE is a SIM user. The device can be placed in the SGSN, MME, RNC or BSC.

FIG. 11 shows an MME in an eleventh embodiment of the present invention.The MME includes: an obtaining unit 1101, configured to obtaininformation about user type or information about a forbidden networktype of a UE, wherein the information about the forbidden network typeindicates the information about a network type that do not allow accessof the UE; and a handling unit 1102, configured to implement handlingaccording to the information about user type or information about theforbidden network type of the UE obtained by the obtaining unit 1101after the UE in the Idle state moves between networks. The handlingincludes: prohibiting the UE from accessing forbidden networks duringlocation update when the UE is a SIM user.

The method for obtaining the information about user type or informationabout a forbidden network type of the UE by the obtaining unit 1101 canbe as follows: obtaining the information about user type or informationabout the forbidden network type of the UE from the context responsesent by the SGSN, or obtaining the information about user type orinformation about the forbidden network type of the UE from the locationupdate message sent by the UE.

In the handling unit 1102, the process of prohibiting the UE fromaccessing forbidden networks during location update can include:rejecting the SIM user from accessing a forbidden network, such aseUTRAN, by sending a TAU rejection message to the UE.

Those killed in the art can complete all or part of the steps in thepreceding method by using a program to instruct the hardware. Theprogram can be stored in a storage medium that can be read by acomputer. When being executed, the program can include the followingsteps: prohibiting a UE that needs to perform network handover fromaccessing a forbidden network if the UE is a SIM user and selecting anaccessible target network for the UE. The preceding storage medium canbe a read-only storage, a disk, or a compact disk (CD).

In the existing technology, when a SIM user communicates in a UTRAN orGERAN network, and moves to a border between an eUTRAN and the UTRAN orGERAN, if the signal strength of the eUTRAN is stronger than that ofother access networks, or in the case of service requirements, thesource network may select the eUTRAN as the target network for networkhandover and switch the user to the eUTRAN temporarily through thenormal handover process. In this case, the SIM user can temporarily usethe resources of the core network and then execute AKA. The SIM,however, does not support AKA. Therefore, if the SIM user is identifiedduring this process, the connection of the SIM user to the eUTRAN isterminated, causing user service interruption. Through the scheme inthis embodiment of the present invention, when the UE needs to performnetwork handover, the UE is prohibited from accessing forbiddennetworks, and an accessible network is selected for the UE beforehandover is complete, thus avoiding service interruption of the SIM userduring network handover and maintaining service continuity. In addition,through the method in this embodiment, the SIM user does not have thechance of using the eUTRAN, thus avoiding security risks in the eUTRAN.The solution in the embodiment of the present invention applies toservice interruption caused by incorrect access to other networks thatforbid access of SIM users in addition to eUTRAN.

The present invention is described through certain preferred embodimentsand drawings. It is understandable that, however, those skilled in theart can make various changes to the forms and details without departingfrom the spirit and scope of the present invention.

What is claimed is:
 1. A method for maintaining user service continuity,comprising: communicating, by a user equipment equipped with a UniversalIntegrated Circuit Card (UICC) of type Subscriber Identity Module (SIM),in a Universal Mobile Telecommunication System Terrestrial Radio AccessNetwork (UTRAN) or a Global System for Mobile communications/EnhancedData rates for GSM Evolution Radio Access Network (GERAN) being a sourcenetwork; sending, by the user equipment, a measurement report to a RadioNetwork Controller (RNC) or a Base Station Controller (BSC) in thesource network, if signal strength of an evolved UTRAN (eUTRAN) isstronger than signal strength of other access networks; performing, bythe user equipment, a handover to a target network other than theeUTRAN; wherein, the target network is selected by the RNC or the BSCbefore the user equipment performs a handover to the eUTRAN.
 2. Themethod according to claim 1, wherein, the target network is selected bythe RNC or the BSC after the RNC or the BSC determines that the userequipment is prohibited from accessing the eUTRAN according to the typeof UICC that the user equipment is equipped with.
 3. The methodaccording to claim 2, wherein, the type of UICC that the user equipmentis equipped with is determined according to information of user type ofthe user equipment received from a source Serving GPRS Support Node(SGSN).
 4. The method according to claim 3, wherein, the type of UICCthat the user equipment is equipped with is determined to be type SIM ifthe user type of the UE is a SIM user.
 5. The method according to claim2, wherein, the type of UICC that the user equipment is equipped with isdetermined according to an authentication vector or user subscriptiondata.
 6. The method according to claim 1, wherein, the UICC of type SIMdoes not support UMTS Authentication and Key Agreement (AKA).
 7. A userequipment for being equipped with a Universal Integrated Circuit Card(UICC) of type Subscriber Identity Module (SIM) used in communicationwith a Universal Mobile Telecommunication System Terrestrial RadioAccess Network (UTRAN) or a Global System for Mobilecommunications/Enhanced Data rates for GSM Evolution Radio AccessNetwork (GERAN) being a source network, comprising: a transmitter,configured to send a measurement report to a Radio Network Controller(RNC) or a Base Station Controller (BSC) in the source network, ifsignal strength of an evolved UTRAN (eUTRAN) is stronger than signalstrength of other access networks; a processor, configured to perform ahandover to a target network other than the eUTRAN; wherein, the targetnetwork is selected by the RNC or the BSC before the user equipmentperforms a handover to the eUTRAN.
 8. The method according to claim 7,wherein, the target network is selected by the RNC or the BSC after theRNC or the BSC determines that the user equipment is prohibited fromaccessing the eUTRAN according to the type of UICC that the userequipment is equipped with.
 9. The method according to claim 8, wherein,the type of UICC that the user equipment is equipped with is determinedaccording to information of user type of the user equipment receivedfrom a source Serving GPRS Support Node (SGSN).
 10. The method accordingto claim 9, wherein, the type of UICC that the user equipment isequipped with is determined to be type SIM if the user type of the userequipment is a SIM user.
 11. The method according to claim 8, wherein,the type of UICC that the user equipment is equipped with is determinedaccording to an authentication vector or user subscription data.
 12. Themethod according to claim 7, wherein, the UICC of type SIM does notsupport UMTS Authentication and Key Agreement (AKA).